Metal working alloy



Patented Jan. l7, 1933 attest WESLEY P. SYKES, OF CLEVELAND HEIGHTS,OHIO, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORKMETAL- WORKING ALLOY No Drawing.

My invention relates to alloys which are suitable for tools and dies andwhich have the property of retaining their hardness at hightemperatures. More particularly, my invention relates to alloys of ironwith metals such as tungsten or molybdenum, or both, and probably themore important class of alloys is that in which the iron predominates.Such alloys are called iron base alloys. As will appear from thespecification and claims, my invention is applicable also to tungsten ormolybdenum base alloys, and also to various other combinations of metalssuch as iron with a hardening metal such as tungsten or molybdenum. Ithas been the accepted opinion that in order to obtain hardness in metalsof this nature, it is necessary to incorporate carbon even wheretungsten and molybdenum are used. I have been able to produce alloys ofiron and tungsten or molybdenum having a very high degree of hardnessand durability under high temperature conditions Where the carbon ispractically absent or present in comparatively low percentages.

According to my invention, as applied to iron base alloys, a body ofsuchmetalsin close association and containing upwards of ten per cent oftungsten, molybdenum or both, is heated up to the temperature at whichtungsten and/or molybdenum goes into solid solution in the iron. Withthe higher percentages of tungsten and molybdenum there will also bepresent a certain quantity of a compound of tungsten or molybdenum withiron. At this temperature the grains of the metal have what is known asthe body centered cubic space lattice structure. The metal is thencooled,rapidly as by quenching, and then raised to an intermediatetemperature at which there is a precipitation of the iron and tungstenor molybdenum compound which is probably iron tungstide or molybdide, ora mixture. I attribute the hardness to the presence of this compounddispersed through the metal body.

My invention is distinguished from the prior art of hardening steelscontaining substantial percentages of carbon in which it is the practiceto heat the steel above what is known as the critical temperature, andthen Application filed October 22, 1926. Serial No. 143,523.

to cool rapidly as by quenching. The critical temperature is thetemperature at which the so-called face centered cubic space latticestructure changes to the body centered cubic space latticestructure, Therapid cooling or quenching produces a fine grained structure which hasbody centered cubic space lattice, the reason for the fine grains beingthat. on account of the quenching, the grains of body centered latticeformed after the transition from the face centered cubic space latticestructure do not have a chance to grow. My invention, on the other hand.does not involve a change of the crystal structure as the metal isalways of the body centered cubic space lattice structure. Accordingtoprior methods, the hardness is obtained by quenching. Any furtherheating and the treatment results in a softening to a certain degree. Onthe other hand in the case of my invention,

the hardness is produced by the aging heat treatment which takes placeafter the quenching.

The following are specific examples of my invention.

Alloys of iron and tzmgsten In these cases the iron may run from ninetyper cent to sixty per cent, the tungsten from ten per cent to forty percent, and the carbon less than one-tenth per cent. For example, an alloycomposed of seventy per cent iron, thirty per cent tungsten, and lessthan twohundredths per cent carbon was prepared by mixing the tungstenand iron in the form of powders obtained by hydrogen reduction of therespective oxides. The mixed powders were pressed into bars one-halfinch by onehalf inch by sixteen inches under a pressure of fifteen toeighteen tons per square inch. One of the bars was heated for one hourat approximately 1500 C. in an atmosphere of hydrogen, and then quenchedin water. The Brinell hardness of this metal was 196, and the Rockwellhardness was C. 15. When this alloy was heatedfor ten hours at atemperature of approximately 700 0., the Brinell hardness had increasedto 460, and the Rockwell hardness to C. 52.

Alloys of iron and molybdenum and carbon below two-hundredths per centwas prepared by mixing the iron and molybdenum powder obtained byhydrogen reduction of iron and molybdenum oxides. The mixture waspressed into bars one-half inch by one-half inch by sixteen inches at apressure of fifteen to eighteen tons per square inch. A bar was heatedin a hydrogen atmosphere at approximately 1410 C. for one hour, and thenquenched in water. After quenching, the Bri-nell hardness of the alloymeasured 214. This bar was then heated for sixty hours at approximately600 C. and this caused the Brinell hardness to increase to 531.

Dies were made from this alloy and heat treated as above described, andthis showed a life many times that of high speed steel dies when usedfor hot swaging of tungsten metal.

A piece of this alloy used a tool bit for turning chromium bearing steelcut four times as much metal as the regular high speed steel tool beforeloslng 1ts cutting edge.

Alloy 30f iron with molybdenum and tungsten These alloys contained ironseventy-five per cent to seventy per cent, molybdenum five totwenty-five per cent, tungsten twenty per cent to five per cent, andcarbon less than onetenth per cent. An alloy composed of ironseventy-three per cent, tungsten five per cent, molybdenum twenty-twoper cent, and carbon below two-hundredths per cent was prepared bymixing the hydrogen reduced metal powders. The mixture was pressed intoa bar five-eighths inches square by sixteen inches at a pressure ofsixteen tons per square inch. A portion of this pressed bar was heatedin a hydrogen atmosphere at about.

14:10 C. for one hour andquenched in water. The Brinell hardness numberof this allo as quenched was 225, and its Rockwell hardness measured C.30. After heating at about 650 C. for four hours, the Brinell hardnesshad increased to 650 and the Rockwell hardness to C. 53.

Microscopic analyses of the important alloys indicate that at 1525 C.about thirtythree per cent of tungsten may be held in solid solution bythe iron. The solubility of the tungsten in iron decreases as thetemperature falls below 1525 C. until at 600 only about eight per centwill be retained in solid solution in the iron. If the tungsten is abovethese percent-ages, the excess is present in patches of what ispresumably the compound iron tungstide Fe W If the temperature of thesolid solution is lowered slowly from 1525 C., the tungsten isprecipitated out in the form of crystals or particles of what ispresumably iron tungstide. The slower the rate of the cooling, the morecomplete will be the precipitation, and the larger will be the size ofthe crystals or particles of precipitated high tungsten compound. If thealloy as quenched from the high temperature, say

from 1525 C., is heated again for several hours at some temperaturebelow 1500 (1, the'precipitation of the tungstide will occur. The sizeof the particles of the precipitate will increase as the temperature ofheating is increased, and also as the time of heating-is prolonged. Forexample, it has been shown by hardness measurements on pieces of alloyscontaining between ten and forty per cent tungsten, the remainder beingiron, that after quenching from 1500 C. and reheating at varioustemperatures between 600 C. and 1400 (l, the maximum increase in Brinellhardness was obtained by heating at approximately 600 C. for as long as300 hours. The hardening effect seems to be less as the temperature ofaging is raised. For example, it is found that upon reheating for onehour at 1200 C. an alloy of twenty-five per cent tungsten and iron afterquenching from 1500 C. no measurable hardening had occurred, If the timeof heating is unduly prolonged, the alloys will begin to soften againafter passing to maximum hardness. It seems from microscopic examinationthat as the size of precipitated particles increases, the hardnessdecreases. It is therefore my theory that the hardening action is due tothe precipitated material which is scattered through the alloys in thehardest state as in particles of sub-microscopic dimensions throughoutthe large grains of the solid solution of tungsten in body centered c icspace latticeiron.

Alloys composed of iron and ten to thirty per cent molybdenum aresimilar in structure to corresponding alloys of iron and tungsten. Atapproximately 1440 C. about twentyfour per cent molybdenum will be heldin solid solution by iron. WVith slow cooling from the 1440 0., what ispresumably thecompound iron molvbdide Fe Mo is precipitated. At 600 C.about seven per cent of molybdenum will exist in solid solution in theiron. When more than four per cent molybdenum is present in the iron,there is no change in crystal structure upon cooling from above 1400 C.to room temperature, the structure being of body centered cubic spacelattice. The maximum hardness is developed in iron alloys containing tento thirty per cent molybdenum after quenching from about1425 C. byreheating or aging at a temperature between 600 C. and 650 C. for aperiod offifteen hours or more. As in the case of the iron tungstenalloys, it is assumed that thehardening is brought about bysub-microscopic particles of the iron mo lybdenum compound precipitatedat the relatively low aging temperature through the coarse grainedmatrix of the solid solution of molybdenum in iron, the latter havingthe body centered cubic space lattice structure.

Instead of agglomerating the metal powders in the preparation of thealloy, the metals may be melted together in a crucible and cast into theshape desired as in the usual practice. The casting may then be heated,quenched and aged as in the case of the agglomerated metal powders.

\Vhat I claim as new and desire to secure by Letters Patent of theUnited States, is:

1. The method of producing substantially carbon free hard alloys of ironwith metal from a group consisting of tungsten and molybdenum whichconsists in heating iron and said metal from a group consisting oftungsten and molybdenum in close association to a temperature at which asolid solution of said metal in the iron will take place, rapidlycooling the body thus formed and finally heating said body to andholding it for at least a few hours at an intermediate temperature,below the initial heating temperature, at which there will be aprecipitation of a compound containing a relatively high percentage ofsaid metal.

2. The method of producing a substantially carbon free hard alloycontaining from about 10% to about 40% of metal from a group consistingof tungsten and molybdenum the remainder of said alloy consistingsubstantially of iron which consists in heating said iron and said metalin close association to a temperature at which a solid solution of saidmetal in the iron will take place, quenching the body thus formed andthereafter raising said body to an intermediate temperature below theinitial heating temperature and holding it at said intermediatetemperature for at least a few hours to thereby produce a precipitationof a compound containing a relatively high percentage of said metal.

3. The method of producing substantially carbon free alloys containingfrom about 10% to about 40% of metalfrom a group consisting of tungstenand molybdenum, the remainder of said alloy consisting substantially ofiron which consists in heating a body consisting of said iron and saidmetal to a temperature necessary to produce a solid solution of saidmetal in the iron, then rapidly cooling as by quenching and afterwardsheating said body to an intermediate temperature below the initialheating temperature and holding it at said temperature for at least afew hours to thereby produce a precipitation of'a compound consisting ofsubmicroscopic particles containing a relatively high percentage of themetal of said group consisting of tungsten and molybdenum.

4. The method of producing a substantial- 1y carbon free hard alloeontainin from about 10% to about 40 o of metal rom a group consistingof tungsten and molybdenum the remamder of said alloy consistingsubstantially of iron which consists in heating a body consisting ofsaid iron and said metal to a temperature above 1400 C.

'but below the melting point of said alloy,

denum the remainder of said alloy consisting substantially of iron whichconsists in heating a body consisting of said 1ron and said metal to atem erature necessary to produce a solid solution of the said metal fromsaid group in the iron,.then rapidly cooling as by quenching andafterwards heating said om a group consisting of tungsten and molybmetalbody to a temperature above 600 C.

but below 1200 C. and holding it at said temperature for at least a fewhours.

6. The method of producing a substantial- 1y carbon free alloycontaining from about 10% to about 40% of metal from a group consistingof tungsten and molybdenum the remainder of said alloy consistingsubstantially of iron which consists in heating a body consisting ofsaid iron and said metal to a temperature above 1400 C. but below themelting point of said alloy,then rapidly cooling as by quenching andafterwards heatin said body to a temperature above 600 and holding it atsaid temperature for'at least a few hours to thereby produce aprecipitation of a compound containing a relatively high percentage ofsaid metal.

7. A hard alloy consisting substantially of iron and metal from a groupconsisting of tungsten and molybdenum, said alloy containing not morethan one-tenth' per cent of carbon, said alloy comprising a structure inwhich sub-microscopic particles of a compound consisting of iron andtungsten and/or molybdenum are distributed throughout said alloy, saidalloy having the property of retaining hardness when used for metalcutting or drawingabove normal temperatures.

8. A substantially carbon free alloy consisting substantially of ironand tungsten or molybdenum said alloy comprising sub-microscopicparticles of iron tungsten or iron molybdenum compound precipitatedthrough a coarser grained matrix of the solid solution of the tungstenor molybdenum in the iron.

9. A substantially carbon free alloy containing at least 60% iron, theremainder of the alloy consisting substantially of tungsten ormolybdenum said alloy comprising submicroscopic particles of irontungsten or iron molybdenum compound precipitated through a coarsergrained matrix of the solid solution of the tungsten or molybdenum inthe iron.

10. A substantially carbon free alloy consisting of at least iron theremainder of the alloy consisting substantially of tungsten ormolybdenum said alloy compr'sing submicroscopic particles of irontungsten or iron molybdenum compound precipitated through a coarsergrained matrix of the solid solution of the tungsten or molybdenum inthe iron.

.11. A hard alloy containing at least 60% iron and less than .1% carbon,the remainder of said alloy consisting substantially of metal from agroup consisting of tungsten and molybdenum, said alloy comprisingsubmicroscopic particles of iron tungsten and/or molybdenum compoundprecipitated through a coarser grained matrix of the solid solution ofthe tungsten and/or molybdenum in the iron.

12.'An alloy substantially carbon free and containing from 60 to 90%iron, the remainder of said alloy consisting substantially of metal ofthe group containing tungsten and molybdenum, said alloy having aBrinell hardness of about 460 or more and having sub-m croscopicparticles of iron tungsten and/or molybdenum compound precipitatedthrough a coarser grained matrix of the .solid solution of the tungstenand /or molybdenum in the iron.

13. The method of producing a substantialthereby form an alloy,quenching said alloy I and reheating the alloy to a temperature of about600 C. or higher but less than 1200 C. for a few hours.

14. An alloy substantially carbon free and containing about 60 to 90%iron, the remainder of the alloy consisting of metal from a groupconsisting of tungsten and molybdenum, said alloy having been heated foran appreciable time at a temperature of about 1500 C. quenched andthereafter aged at a temperature of about 600 C. or hi her but less than1200" 0., said alloy beingcharacterized by a structure in whichparticles of an iron tungsten or iron molybdenum compound aredistributed through said alloy.

15. An alloy substantially carbon free and containing about 60 to about90% iron, the remainder of the alloy-consisting of a metal from a groupconsisting of tungsten and molybdenum, said alloy having been heated ata temperature above 1000 C. but lower than the melting point of saidalloy, quenched and thereafter aged at a temperature of about 600- C. orhigher but less than said first mentioned temperature to thereby causeprecipitation of an iron molybdenum or iron tungsten compound throughsaid allow.

16 The method of producing a hard, substantially carbon free alloyconsisting substantially of metal of the iron group and metal from agroup consisting of tungsten and molybdenum which comprises heating saidmetals in close association to a temperature above 1000 but lower thanthe melting point of the alloy, quenching the body thus formed andthereafter heating said body at an intermediate temperature below theinitial temperature to thereby cause precipitation of a compound of saidmetals throughout said body, said precipitated compound being inparticles of submicroscopic dimensions.

17 The method of producing a substantially carbon free alloy consistingsubstantially of metal from a group consisting of tungsten and.molybdenum and metal of the iron group said metal of the iron groupcomprising the main constituent of said alloy, said metal from the groupconsisting of tungsten and molybdenum comprising from about 10% to about40% of said alloy, which comprises heating saidmetals in closeassociation to atemperature at which a solid solution of said metal fromthe group'consisting of tungsten and molybdenum in said metal of theiron group will take place, rapidly cooling the body thus formed andfinally raising it to an intermediate temperature below the initialheating temperature and holding it at said intermediate temperature tothereby precipitate a compound consisting of sub-' mlcroscopic particlescontaining a relatively metal from a group consisting of tungsten andmolybdenum, said metal of the iron group forming the main constituent ofsaid alloy and said metal of the group consisting of tungsten andmolybdenum comprising from a out 10 to about 40% of said alloy, whichcomprises forming said metals into a coherent mass, heating said mass toa temperature between about 1400 and about 1500 Ci quenching the massand reheating it at an intermediate temperature, below the initialheating temperature, at which there will be a precipitation of acompound containing a relatively high percenta e of said metal from agroup consisting oftungsten and molybdenum.

19. The method of producing a hard, substantially carbon free alloyconsisting of about 10 to 40% of metal from a group consisting oftungsten and molybdenum, the remainder of said alloy consistingsubstantially of metal of the iron group which comprises forming saidmetals into a coherent mass, heating said mass to a temperature betweenabout 1400 and 1500 0., quenching the mass, reheating it to anintermediate temperature below the initialheating temperature andholding it at said intermediate tem- 1 perature to thereby produce aprecipitation of a compound consisting of sub-microscopic particlescontaining a relatively high percentage of said metal from a groupconsisting of tungsten and molybdenum. 20. A hard, substantially carbonfree alloy consisting mainly of iron but containing at least 10% ofmetal from a group consisting of tungsten and molybdenum, said alloycomprising a structure in which sub-microscopic particles of a compoundconsisting of iron and tungsten and/or molybdenum are dis tributedthroughout said alloy, said alloy having the property of retaininghardness when used for metal cutting or drawing above normaltemperatures.

21. A hard, substantially carbon free metal body contaimng about 10% toabout 40% of metal from a group consisting of tungsten and molybdenum,the remainder of said metal body consisting substantially of metal fromthe iron group, said metal body comprising sub-microscopic particles ofa compound of said metal of the iron group and said metal from the groupconsisting of tungsten and molybdenum precipitated throughout said metalbody.

22. A substantially carbon free alloy containing about 10% to about 40%of metal from a group consisting of tungsten and 40 molybdenum theremainder of said alloy consisting substantially of metal of the irongroup, said alloy having been heated at a temperature at which solidsolution of the tungsten and/ or molybdenum in the metal of the irongroup will take place, quenched and thereafter aged at an intermediatetemperature below the initial heating temperature to thereby causeprecipitation of a compound of said metal of theiron group and saidmetal of the group containing tungsten and molybdenum throughout saidalloy.

In witness whereof, I have hereunto set my hand this 18th day ofOctober, 1926.

WESLEY P. SYKES. 65

